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Nature: Mice play main role between plants, predators in every terrestrial ecosystem

Sunday, November 14, 1999

By Scott Shalaway

Ecology textbooks often illustrate energy flow through an ecosystem with diagrams called ecological pyramids. Whether depicting weight or numbers of organisms at each feeding level, an ecological pyramid lumps all the primary producers (plants) at the base of the pyramid. Plants form the foundation of virtually all such diagrams. The second level is necessarily smaller since it is sustained by plants, and consists of herbivores or plant-eating animals, such as deer, rabbits and many rodents. Above the herbivores sit first order predators, such as snakes. And above snakes sit hawks, owls and other top carnivores.

 
 

Send questions and comments to Scott Shalaway, R.D. 5, Cameron, WV 26033, or via e-mail to sshalaway@aol.com, and catch Scott on the radio Monday through Friday from 4 to 6 p.m. on 730 WPIT-AM.

   
 

The importance of plants in any ecosystem is evident from any ecological pyramid. The role of herbivores may be secondary, but is equally critical. Without the pyramid's second tier, there would be no predators and hence no animal community.

Among the most important herbivores in almost any ecosystem are mice. In forests, fields, farmlands and backyards, mice sustain predators of all sizes. They link plants and predators in every terrestrial ecosystem. Mice sustain weasels, foxes, coyotes, hawks, owls, skunks, shrews, bobcats and bears. Name a predator, and it probably eats mice.

But not just one generic mouse supports the nature's complex webs of life. A surprising diversity of mice roam local fields, forests, and even kitchen cupboards and counter tops.

Lest we overlook the keystones of every ecological pyramid, here's a brief look at the seven most common and widespread mice. Unless you live in the heart of downtown, at least five and maybe all seven live within a 100-yard radius of your living room. Most weigh less than one ounce, and their populations can range from one to hundreds per acre.

Deer mice and white-footed mice (members of the genus Peromyscus) are twins that even mammalogists have trouble telling apart. They are cute, classic mice -- brown fur, white bellies, long tails, prominent ears and big black eyes.

Peromyscus live in old fields, forest edges and in the woods itself. They are equally at home in underground burrows, tree cavities and bird houses. Most of my nest boxes house these mice all winter long, often in heat-conserving social groups of three to five individuals. (Beware when cleaning out dusty mouse nests. Peromycus harbors the potentially fatal hanta virus. Do not inhale Peromyscus dust.)

Meadow voles and woodland voles (members of the genus Microtus) stick to within several inches of ground level. Small beady eyes, tiny ears concealed by fur and short tails characterize these shaggy little mice.

Meadow voles require the protective layer of dead grass that unmowed, ungrazed fields and meadows provide. There they maintain inch-wide runways that crisscross their territories.

Woodland voles, as their name implies, are more at home on the forest floor. Thanks to large front feet adapted for digging, they spend most of their time in the protective confines of a subterranean subway system.

Southern bog lemmings, meadow jumping mice, and house mice round out the rodent roster.

Poorly named bog lemmings occupy old fields and woodland clearings as well as wet meadows. They only require a thick mat of dead grass to conceal their vole-like comings and goings. The bog lemming's distinguishing feature is a prominent groove on the side of each upper incisor.

Jumping mice are long-tailed rodents with two distinct features -- huge hind feet responsible for their hopping ability and deeply grooved upper incisors. Predators find them on the ground in old fields, thickets and along forest edges. Jumping mice are the only true hibernators of the group and will soon retire for the winter.

House mice need little introduction. The naked ears, pointy snout, and scaly tail are familiar to anyone who has ever set a mouse trap. As the name implies, this Old World import thrives in our midst.

Though rarely appreciated, mice are the tie that bind plants to carnivores in every terrestrial ecosystem.



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